1,166 research outputs found
Cohomology of Conformal Algebras
Conformal algebra is an axiomatic description of the operator product
expansion of chiral fields in conformal field theory. On the other hand, it is
an adequate tool for the study of infinite-dimensional Lie algebras satisfying
the locality property. The main examples of such Lie algebras are those
``based'' on the punctured complex plane, like the Virasoro algebra and loop
algebras. In the present paper we develop a cohomology theory of conformal
algebras with coefficients in an arbitrary module. It possesses standard
properties of cohomology theories; for example, it describes extensions and
deformations. We offer explicit computations for most of the important
examples.Comment: 46 pp., AMSLaTeX, uses epsfig, amssymb, amsc
Q-phonon description of low lying 1^- two-phonon states in spherical nuclei
The properties of 1^-_1 two-phonon states and the characteristics of E1
transition probabilities between low-lying collective states in spherical
nuclei are analysed within the Q-phonon approach to the description of
collective states. Several relations between observables are obtained.
Microscopic calculations of the E1 0^+_1 -> 1^-_1 transition matrix elements
are performed on the basis of the RPA. A satisfactory description of the
experimental data is obtained.Comment: 16 pages, 2 figures, 9 table
Reduction of quantum noise in optical interferometers using squeezed light
We study the photon counting noise in optical interferometers used for
gravitational wave detection. In order to reduce quantum noise a squeezed
vacuum state is injected into the usually unused input port. Here, we
specifically investigate the so called `dark port case', when the beam splitter
is oriented close to 90{\deg} to the incoming laser beam, such that nearly all
photons go to one output port of the interferometer, and only a small fraction
of photons is seen in the other port (`dark port'). For this case it had been
suggested that signal amplification is possible without concurrent noise
amplification [R.Barak and Y.Ben-Aryeh, J.Opt.Soc.Am.B25(361)2008]. We show
that by injection of a squeezed vacuum state into the second input port,
counting noise is reduced for large values of the squeezing factor, however the
signal is not amplified. Signal strength only depends on the intensity of the
laser beam.Comment: 8 pages, 1 figur
Digital twins in logistics
The logistics industry has undergone significant transformation over the years, thanks to advancements in technology. One of the most promising technologies disrupting the industry is digital twins. In this article, we explore the concept of digital twins in logistics, their benefits, and their potential impact on the industry
Kinetic-inductance-limited reset time of superconducting nanowire photon counters
We investigate the recovery of superconducting NbN-nanowire photon counters
after detection of an optical pulse at a wavelength of 1550 nm, and present a
model that quantitatively accounts for our observations. The reset time is
found to be limited by the large kinetic inductance of these nanowires, which
forces a tradeoff between counting rate and either detection efficiency or
active area. Devices of usable size and high detection efficiency are found to
have reset times orders of magnitude longer than their intrinsic photoresponse
time.Comment: Submitted to Applied Physics Letter
On the chromatic numbers of 3-dimensional slices
We prove that for an arbitrary holds where stands for the chromatic
number of an (infinite) graph with the vertex set and the edge set consists
of pairs of monochromatic points at the distance 1 apart
Ground state correlations and structure of odd spherical nuclei
It is well known that the Pauli principle plays a substantial role at low
energies because the phonon operators are not ideal boson operators.
Calculating the exact commutators between the quasiparticle and phonon
operators one can take into account the Pauli principle corrections. Besides
the ground state correlations due to the quasiparticle interaction in the
ground state influence the single particle fragmentation as well. In this
paper, we generalize the basic QPM equations to account for both mentioned
effects. As an illustration of our approach, calculations on the structure of
the low-lying states in Ba have been performed.Comment: 12 pages, 1 figur
Coherent states of non-relativistic electron in magnetic-solenoid field
We construct coherent states of a nonrelativistic electron in the
magnetic-solenoid field, which is a superposition of the Aharonov-Bohm field
and a collinear uniform magnetic field. In the problem under consideration
there are two kind of coherent states, the first kind corresponds to classical
trajectories which embrace the solenoid and the second one to trajectories
which do not. Mean coordinates in the constructed coherent states are moving
along classical trajectories, the coherent states maintain their form under the
time evolution, and represent a complete set of functions, which can be useful
in semi classical calculations. In the absence of the Aharonov-Bohm filed these
states are reduced to the well-known in the case of uniform magnetic field
Malkin-Man'ko coherent states.Comment: 11 pages, version accepted for publication in J. Phys. A, 3 figures
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